DE2114234A1 - Graphic data recording and integration arrangement - Google Patents

Description

LABORATORY DATA CONTROL, INC., Interstate Industrial Park,

Riviera Beach, Florida, U.S.A.

Graphic data recording and integrating arrangement.

The invention relates to graphic data recording arrangements, esp. chart recorder data integrators, in which the area below a chart recorder Curve is continuously calculated, and in which the area information is displayed on the edge of the curve sheet will.

It is often desirable to determine the area under a curve, or part of a curve, by means of a chart recorder is recorded. An example of such an application is gas or vapor chromatography, where curve recording shows a series of peaks, each representing a component of the sample that has a different molecular weight owns. The area under each peak is a measure of the existing size of the corresponding elutent from the chromatograph column.

The desired areas can be measured on the curve with the help of a planimeter. There is a faster method however, in using an automatic integrator coupled to or built into the chart recorder. A

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such known integrator uses an analog computation mechanism, namely a so-called ball friction disk drive. This mechanism is designed so that the speed of its Output shaft is proportional to the deflection coordinate of the main recording pen. This shaft turns a cam, which causes an auxiliary pen to create a zigzag line or draws a triangular wave along the lower edge portion of the curve. The spatial frequency of this wave is proportional the main pen ordinate; thus the number of periods in a given interval is proportional to the Area below the main curve. The area is obtained by counting the periods in the desired interval.

The present invention provides an improvement over such known arrangements, which is much more versatile and cheaper and easier to manufacture can.

According to the invention there is provided an integrating arrangement for chart recorders suggested making an auxiliary lane on the curve sheet records from which the areas under a desired part of the main curve by counting the corresponding number of periods can be determined.

Instead of a mechanical integrator, an electrical pulse generator is used according to the present invention, its Output frequency (or repetition rate) proportional to the electrical Input signal to the recorder. The pulse generator or voltage-frequency converter controls a stepper motor via an additional circuit. The motor in turn drives a cam. This cam moves the auxiliary pen forwards and backwards and creates a zigzag or triangular curve on the curve sheet that contains the area information indicates.

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The output of the pulse generator can also be an electrical one operated meters are supplied. The output of the pulse generator can also be recorded on a magnetic tape, for example will. This pulse record can later be used to create the original analog curve sheet record reconstruct using an appropriate facility; or it can be fed into a digital computer for analysis or comparison with other such records.

The invention provides a preferred form of electronic circuitry for generating the pulses and controlling the An embodiment of the novel voltage-to-pulse rate converter circuit gives a very stable and linear conversion in a unipolar way, i.e. the pulse rate is zero, when the input control voltage is zero and precisely proportional to the input control voltage of one polarity; are entrances opposite polarity are present, no pulses are generated.

The invention is explained below in conjunction with the drawing using an exemplary embodiment. The figures show:

Fig. 1 is a schematic representation of a chart recorder and integrating arrangement according to the invention, with essential Parts of the arrangement are shown in the block diagram,

Fig. 2 is a detail of part of an integrator record;

Fig. 3 is a schematic circuit diagram of part of the circuit for controlling the converter, the voltages in frequencies converts,

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4 shows a detailed schematic representation of a preferred embodiment of the voltage-frequency converter and the associated circuit for controlling the stepping motor and

5 shows a schematic representation of another embodiment of a cam control for driving the integrator writing device.

Fig. 1 shows schematically a chart recorder with an integrating device according to the present invention. Part of a

P curve sheet, e.g. of a conventional recording strip made of paper, denoted by 1; a part of a recording or track 2 is plotted on it, this recording by means of a marking element 3 *, e.g. a recording pen is. The marking device 3 can be mounted on a carrier 4 which is movable in a direction transverse to the curve sheet 1 and arranged with the help of an elastic cable 5 on rollers 6, 7, or by any other Mechanism that is slidable. The marking device 3 can be moved via a servo drive 8, which is mechanically with one of the rollers 6 is connected, for example in the form of a corresponding joint, as indicated by dashed lines 14

* tet is. Along the main track 2 on the curve sheet 1 is one Auxiliary track or integrator track 22 in the form of a zigzag line or a triangular wave with a changing period. This track 22 takes the integrator information on. It can be recorded with an auxiliary marking device 23 which can be referred to as an integrator recording device, and which can be designed as a pen. The pen 23 can be connected to an arm 24 articulated at 25 A cam follower 26 is arranged on the arm 24, for example. The driver 26 follows a cam 27, which is designed so that it results in a deflection of the pen 23, which is approximately linear with respect to the angle of rotation. Of the

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Cam 27 is controlled by a stepper motor 28, 28 'via a 44 indicated connection driven; A transmission gear can be used between the motor 28 and the cam 27.

In the electrical part of FIG. 1, the servomotor 8 receives its drive energy from an amplifier 9. The input circuit to the amplifier 9 contains a battery or other constant voltage supply source 10 and a sliding wire potentiometer 11, which is connected so that the output voltage e of the potentiometer 11 counteracts the input signal voltage e, which is applied to the main input terminals 40, 41. The motor 8 drives the potentiometer or the sliding wire 11 as well as the pen 3 via schematically indicated by 13, 14 Linkage on. When an input voltage e- is applied to terminals 40, 41, part of this voltage occurs the amplifier input terminals 19, 20 via the resistor 17. The potentiometer voltage e also occurs at these same terminals 19, 20 with opposite polarity across the resistor l8. When the resulting differential voltage is not zero, it is amplified and the amplifier 9 drives the servo motor 8 in a direction that the difference to Becomes zero. The position of the slide of the potentiometer 11 is then a measure of the size of the input voltage e, and is recorded by the pen 3 so. This represents the operation of a potentiometer zero balance recorder known type. In practice, the resistors 17, 18 can be very largely different, so that one high voltage e can balance a small input e. For example, if the resistor 17 has a value of 500 ohms and the resistor 18 has a value of 500,000 ohms, a voltage e of 5 V is approximately equal to an input e of 5 mV

sr - ^ *

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In the integrator part of the arrangement, a voltage which is a function of the potentiometer voltage e is applied to the input terminals 30, Jl of the voltage-frequency converter 29 is supplied. This Converter generates electrical pulses that appear at a pulse output terminal 33. The repetition rate is a linear function the DC control voltage at the converter input terminals 30, 31 · These pulses can be fed into a counter 3 ^ e.g. a magnetically operated display counter or write counter. During a certain interval the Count proportional to the area under the corresponding part of curve 2. The pulses can also be recorded on a magnetic tape recorder or a corresponding device 35 can be recorded.

The function of the potentiometer voltage e applied to the converter terminals 30, 31 occurs is linear, with one suppressed Zero point or reference level. This reference level is set by a potentiometer 12 in a known manner, and the The inclination of the function is set by a potentiometer 36.

Another output of the transducer 9 is a square wave shape; it occurs at the output terminals 37 * 38, 39. He is connected to the tracks 28 ′ of a stepping motor, the rotor of which is designated by 28. This motor drives the cam 27 in in the manner described. The rectangular curve obtained from the pulses is synchronous with them. Of the Motor 28, 28 'advances one step with each pulse. The mean speed of the motor is therefore proportional the control voltage at terminals 30, 31

The term "stepper motor" includes any device, sequential There is an increase in the movement as a function of individual impulses, half-periods or periods. Various known stepper motors move, for example

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by 12 ° for each input period. There are known solenoid operated ratchet devices to perform the same function.

With respect to the part of the curve sheet shown in FIG. 1, the integrator curve 22 is interpreted in the following way. It is assumed that the area under the part of the curve which lies between points a and b is to be found. A projection is then made from these points to the points a ¹ and b 'on the integrator track 22 and the number of half-periods or deflections between them is counted, for example 9-1 / 2; this represents the desired area. The number is of course relative, but can be calibrated in known experiments in, for example, a gas chromatograph.

For further explanation, on track 2 between points c and d, voltage e is zero, and motor 28 is running thus not around, and this part of the track is horizontal. At the opposite point e is the speed of the motor 28 relatively large, so that the periods of the integrator track 22 are relatively close to one another. If dy / dt the Inclination of the track 22 and ρ is an ordinate of the curve 2, as shown in Fig. 1, applies

dy / dt = ρ = I y dt, where constants are neglected will.

Fig. 2 shows part of another integrator track 22 'im individual: this figure shows more clearly how part of a period or a deflection is measured. That Curve sheet can be printed with ten parallel lines 42, for example. Has between points g and h (Fig. 2) the curve 22 'crossed ten such lines, so that the dimension of the area is 10/10 = 1. On the other hand, the relationship can

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of gear 45 and constants of the converter 29 are selected so that an appropriate number of, for example ten steps of the stepping motor 28, 28 ^f results in a deflection (half period) of the pen 23. The steps are then visible in the track 22 ', as indicated by 43, and can be counted.

A voltage-frequency converter 29 is relatively simple and practical construction usually makes one full-scale DC input or control voltage of several True magnitude volts required. In the case of a recording device working with a potentiometer, the method described in Pig. I kind shown the main chi e wire 11 often has such a tension of e.g. 5 volts, which are maintained on it by a supply source 10 will; thus the control voltage for the converter 29 taken directly from the output e of the sliding wire 11 as is the case in FIG.

In some recording devices with a potentiometer, however, there is a much lower voltage, e.g. 10 mV, on the main loop wire. In such devices, an additional potentiometer is usually provided as a tracking loop wire and which is mechanically coupled to the main slip wire. To the integrator according to the invention in such In order to be able to use devices, the converter 29 can be controlled from the Mitl to the chip, as shown in FIG is.

In this Fig. 3 is the slide of the tracking slip wire 51 mechanically with the main slip wire of a (not shown) Mechanically coupled writer, as indicated by the dashed line 54. A suitable DC voltage, for example 5 volts is generated on the sliding wire 51 by a supply source of any kind via resistors 52, 53. The adjustable one Resistor 52 is provided for a zero setting, and a

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Potentiometer 56 for setting the gain or the Inclination of the converter function, as is known per se. The supply source 55 may be the same as the supply source is the circuit for converter 29 which generates 20 volts, for example. The voltage on the tracking loop wire 51 can be over the resistor 52 can be reduced to five volts, for example. The ground connections at the supply source 55 * at the resistor 52 and on the converter 29 (at 57) can be implemented together.

In the more general case where the tension is on the main slip wire is relatively large, as in FIG. 1, it is necessary to use an ungrounded supply source on the converter 29. This is the arrangement shown schematically in FIG. The converter circuit is the same for each type of recorder; the difference is that ii> the first case a Side of the converter supply source 90 (Fig. 4) is grounded, in in the latter case (Fig. 1) not.

In the circuit according to FIG. 4, the pulse generator part of the switching arrangement has transistors 61-64, the pulse output takes place at terminal 33 «The pulses from this point are passed through a small capacitor 84 to a square wave multivibrator out, the transistors 65 and 66 has. These become conductive alternately and with each impulse in a transition controlled. The square wave frequency is thus half of the W recovery rate of the pulses. This multivibrator for his part controls two power transistors 67, 68 in emitter follower circuit. The emitters are with output terminals 37 * 38, 39 connected, which in turn are connected to the stepping motor, which actuates the motor directions 28 'step by step.

The circuit of FIG. 4 will now be considered in detail. The transistor 6l is a constant current element in

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switched in a known manner. Its collector current is set with the aid of the adjustable emitter resistor 70. In conjunction with the time-determining capacitor 71, this current determines the pulse repetition rate for a given control voltage which is applied to the input terminals 30, 31. The collector of the current element transistor 61 feeds the base of a transistor amplifier stage 62, the emitter of which is grounded (the negative or common side of the supply source 90 is regarded as "grounded", regardless of whether it is connected to ground or not), and which has a collector load resistor 72 . This stage feeds a second, similar stage 63, 73 * 81 via the coupling capacitor 74. This capacitor determines the length of each pulse and has a relatively small capacitance, since the pulses should be fairly short. The final stage of the pulse generator circuit is an emitter follower circuit 64 with an emitter load resistor 82. The relationship between control voltage pulse repetition rate in this circuit is very linear and precise _"s that can be tolerated in many cases In a small loss of linearity, the emitter follower stage 64 may , 82 are omitted. The time-determining capacitor 71 * the output terminal 33 and the coupling capacitor 8.4 are then connected to the collector of the transistor 63 at the point 85.

At 86, near the input terminal 30, there is a temperature compensation diode shown. This is in -di «series connection to the base-emitter connection of the transistor 61. If you consists of the same semiconductor material as the transistor 61, e.g. of silicon, it serves to set the direct current operating point of the transistor 6l to compensate for temperature changes as effectively as the more conventional arrangements in which two transistors can be used in a differential amplifier or in a cathode-coupled push-pull stage.

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An essential property of this circuit is that the pulse rate is zero, i.e. the circuit is not oscillates when a control voltage at terminal 31 exceeds the value Has zero or is negative with respect to terminal 30. Only if it is positive, pulses are generated, the rate being proportional to the control voltage.

The square wave multivibrator circuit 65, 66 , etc. is of conventional design. The collector of transistor 65 is cross-coupled to the base of transistor 66 via resistors 79, 8D, and the collector of transistor 66 is similarly coupled to the base of transistor 65 via resistors 77 * 78. A resistor 87, with which the control pulses from the pulse generator are coupled via the capacitor 84, is jointly assigned to the collector circuits 75 * 76.

The collectors of the transistors 65, 66 are coupled directly to the bases of the output stage 67 * 68, which are the stepper motor windings 28 * control in a conventional manner.

The pulse generator circuit operates in the following manner: Assume that device 63 is just turned off and that points 85 * 33 are raised approximately to positive supply voltage have been. Capacitor 71 is across resistor or device 64 (or resistor 81, if the device 64 has been omitted in the manner described), and via the base-emitter connection of the device 62 has been charged. When the capacitor 71 is fully charged, the device 62 begins to turn off, whereby the device 63 suddenly becomes conductive. The left side of the capacitor 7I now takes a negative potential on and turns off the device 62 completely. The charge now flows relatively slowly over the current element 6l at a speed determined by the control voltage

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the terminals 30, Jl and the setting of the resistor 70 is determined from. The discharge duration is the interval between pulses. When the capacitor 71 has been sufficiently discharged, the device 62 becomes conductive and switches the device 63 off $ then the cycle repeats. When the emitter follower 64 is used, the capacitor J1 charges faster and it is found that the relationship of the pulse rate to the control voltage becomes more linear.

The circuitry containing the devices 65, 66 is a bistable multivibrator of known embodiment. One device is conductive and the other is current blocking. The punctures are reversed when a pulse is applied across capacitor 84 to the collector circuit. Thus, the frequency of the square wave generated by devices 65 * 66 is half the repetition rate of the pulses.

A counter 34 of suitable embodiment can be obtained from the pulse output terminal 33 are fed to allow the area under any part of curve 2 (Fig. 1) during which it is effective is digitally displayed. The counter 34 can do so be able to print out the numbers.

The pulses can also be recorded, for example using a magnetic writer 35 according to FIGS. The information on the graphical curve, e.g. 2,. ■ can be much more compact on a magnetic tape or the like. As is the case by storing the curve sheets 1 themselves. Consequently it is desirable to have large numbers of curves, e.g. gas = - Ehromatograms to save in this way. You can in graphic recordings are reconverted, if so desired, by placing the tapes in a pulse rate discriminator and then into a graph chart recorder

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can be imported in a conventional manner. In addition, the Tape data are stored in the memory of a computer. The calculator can be programmed to spike or Retrieves groups of peaks that are stored and compares them to the pulse data on an unknown tape; thus unknown substances can be identified by taking pulse recordings of their chromatograms fed into a computer with a corresponding "library" of stored data and a suitable Program is provided. Methods of this type can be carried out with the invention, but not with integration arrangements known species.

In Fig. 5 is a modification 27 ^! of the cam 27 (Fig. 1) in connection with an associated arm 24 ', a writing pen 23, a cam follower 26 and part of an integrator track 22 shown in dashed lines. The difference is that the cam 27 * has a tab which is distinguished by a slight difference in height, so that certain periods of the track 22 ^f are emphasized for easier counting. In Fig. 5, a cam with five tabs is shown at 27 *, a tab 91 'is emphasized. In track 22 * every fifth cycle 9I is slightly higher than the others. A cam with a different number of lobes, for example three, can also be used.

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Claims (10)

21H234 17-3.1971 W / He - l4 - L / p 7090 Claims; Graphic data recording arrangement, characterized by a recording device with a device for marking an analog trace of an electrical input signal on a curve sheet, a converter which converts a function of the signal into electrical pulses of an analog repetition rate, a control circuit which is controlled by the converter and an integrator motor device drives, and a cam device connecting the integrator motor device to an auxiliary marking element for marking an oscillating integrator track along a portion of the cam. 2. Arrangement according to claim 1, characterized in that the recording device is a zero adjustment potentlometer recording device with a servo motor that drives a marking element and an abrasive wire, and that the puncture is adjustable Voltage dividers, which are connected to the squint wire, derived will. 3 · Arrangement according to claim 1, characterized in that the Recorder a zero balance potentiometer recorder is with a servo motor drive that drives a marking element, a main slip wire and a trailing slip wire, and that connections from the tracking loop wire to an input circuit of the converter are provided. 4. Arrangement according to claim 1, characterized in that the converter comprises a first active semiconductor device which has an input terminal and is connected as a controlled current stage that a second and a third active semiconductor device are connected as amplifier stages with a capacitive coupling, and that a feedback connection is provided via a time-determining capacitor from the third device to an output terminal of the first device. 209810/1044 21U234 3/17/1971 W / He - 15 - L / p 7090 5. Arrangement according to claim 4, characterized in that one Emitter follower between an output terminal of the third device and the feedback connection is switched. 6. Arrangement according to claim 1, characterized in that one Pulse output terminal is connected to an output of the converter and that a counter is connected to the terminal. 7. Arrangement according to claim 1, characterized in that a pulse output terminal is connected to an output of the converter and that a recorder is connected to the terminal to record the pulses. S. Arrangement according to claim 1, characterized in that the cam device has a cam which is designed so that it moves the auxiliary marking element as a linear function of the angular displacement of the cam, the integrator track represents a triangular waveform of constant peak amplitude and changing slope, and that the number of oscillations of the wave is proportional to the area below the analog track. 9 «arrangement according to claim 1, characterized in that the Cam device comprises a cam which is designed so that it the auxiliary marking element as a linear function of the angular displacement of the cam shifts, and that the integrator drive is a stepper motor, which is in a fixed increment is moved for each pulse, where the integrator track is a triangular wave with steps, and where fractions of a half Period of the wave can be measured by counting the steps. 10. The arrangement according to claim 8, characterized in that the cam device has a cam with a plurality of tabs, at least one of which has a shape different from the other, with the corresponding periods the many are emphasized to simplify their counting. 209810/1044